Abstract: In the present thesis, I investigate the hierarchical structure of morphometric and molecular diversity within and between the Nordic dogroses (Rosa Sect. Caninae, Rosaceae). I also investigate patterns of geographic differentiation and taxonomic relationships within the group. The dogroses are characterized by a unique genetic system, the so-called ”canina meiosis” that leads to an uneven allocation of maternal and paternal chromosomes to the progeny and results in a largely matroclinal mode of inheritance. The partitioning of morphometric and molecular diversity in the investigated taxa was similar to that found in selfing or apomictic species. However, because of the matroclinal effects of the canina meiosis, the partitioning of morphometric and molecular diversity within the dogrose taxa cannot be simply interpreted in terms of different levels of selfing or apomixis. Most of the investigated Sect. Caninae taxa show a somewhat mosaic pattern of geographic differentiation between populations in both leaflet shape and reproductive characters. Two of the taxa (R. dumalis subsp. dumalis and R. rubiginosa) show weak geographic differentiation in one of the character sets: R. dumalis subsp. dumalis in leaflet shape and R. rubiginosa in reproductive characters. The Nordic dogroses can be divided into three distinct groups: the R. canina group, the R. rubiginosa group and the R. villosa group, on the basis of morphology and RAPD marker variation. Neither morphometric or molecular data support the present delimitation of subspecies within R. dumalis and the variation within R. dumalis might be better described at a lower rank than that of subspecies. Morphometric data support the current taxonomic separation between R. villosa subsp. mollis and R. sherardii and the varietal subdivision of R. sherardii.